1. Field of the Invention
Embodiments of the present invention relate to a self-aligning cutter hub, and specifically to a self-aligning cutter hub assembly for use in a pelletizer such that the blades thereon are in proper alignment with the die face of the extrusion die plate of the pelletizer.
2. Description of the Prior Art
Underwater pelletizers for forming pellets typically use an extrusion die with orifices through which molten polymer is extruded. Specifically, the molten polymer is extruded out from a die face, wherein cutter blades mounted on a rotatable cutter hub cut the plastic “ribbons” into pellets. The cutter hub is generally driven by a drive shaft. The cutter blades (and thus the hub) are preferably aligned such that the blades themselves are substantially parallel to the die face. In this manner, the pellets are substantially uniform in shape, i.e., the pellets from a first side of the die face are not larger than pellets from a second side of the die face due to a misalignment.
As a result, it is desirable to maintain the cutter blades and die face in properly aligned relation so that the cutting edge of the blades on the rotating cutter hub move in very close parallel relation to the die face. This close parallel relationship enables the blades to efficiently cut the extruded plastic into pellets as the plastic strands are discharged from the orifices in the extrusion die plate. As mentioned above, parallel alignment also enables the production of substantially uniform pellets. Additionally, proper alignment prevents unnecessary wear of the cutter blade and/or die plate face due to interference between the two and unnecessary side loading on bearings and shafts.
It is also desirable to be able to separate the cutter head from the die plate to enable, for example and not limitation, cleaning and maintenance, blade replacement, and inspection. Upon reassembly, however, the cutter head must be realigned with the die face. Conventional configurations have often relied on manual alignment of the cutter with the die face. Unfortunately, manually realigning the cutter head every time the machine is serviced requires a skilled worker, a substantial amount of time, and requires expensive and complicated adjustment means.
What is needed, therefore, is a system and method that provides accurate alignment of the cutter head and die plate that is simple and robust. The system should provide good serviceability and performance with relatively low equipment and maintenance costs. It is to such a system that embodiments of the present invention are primarily directed.